Amol,
For larger BGAs that T is necessary to get good solder joints underneath the BGA die—that is why you have a trend towards vapor phase.
Werner
-----Original Message-----
From: Amol Kane <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, Mar 17, 2011 9:19 am
Subject: Re: [TN] Query on failure of assembled PCB
Did you say reflow with a peak of 262C??...that's excessive by even lead-free
standards. Most lead-free components are rated to only 260C. a peak reflow
temperature of 235C to 245C should suffices in a majority of cases.
Amol Kane | Process Engineer
Catalyst Manufacturing Services, Inc.
941 Route 38, Owego NY 13827
Phone: (607) 687-7669 Extn 349 | Website: www.catalystems.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj
Sent: Wednesday, March 16, 2011 10:28 PM
To: [log in to unmask]
Subject: [TN] Query on failure of assembled PCB
Dear All,
1. We are manufacturers of PCBs. One of our customer has reported
failure in assembled boards. The main observation is that after
assembly, the assembled units were functioning normally
and had passed all the stipulated electrical tests. These parts
were kept at the assembly house for around over 3-4 months. Later
when the assembled units were scheduled to be integrated into
the system, the assembled units were tested again, but now they
see failure.
These are the inputs given to us..........
a) Failures are intermittent in nature.
b) Failures are concentrated in and around the area where
BGA is mounted.
c) Some failures are recovered by applying mechanical stress on
the PCB.
d) Some are recovered by subjecting to reflow.
e) There are no component failures.
2. Our customer's assembly process flow is…
a) 100Deg C, 16 hours baking
b) Assembly done within 24 hours after baking
c) Pb-free reflow conducted with a peak temperature of 262Deg C
d) Reflow is done 2 times (once for each side of components)
e) Visual and physical inspection done
f) Cycling done at -20~+70Deg C for 10 cycles. First 9 cycles
are 30minutes per cycle and the last cycle is 1 hour cycle
g) Electrical testing
3. We had retrieved a blank PCB from the same batch and conducted
the following trial......
a) A standard step of baking prior to assembly (100Deg C,
16 hours baking) was skipped due to time constraint.
b) 2x reflow done at customer's place using standard profile
used for assembly of this part.
Electrical Testing (BBT) on bare PCB passed .
c) 10 cycles of temp. cycling done at customer's place using the
standard cycling profile used for assembled unit.
Electrical Testing (BBT) on bare PCB passed .
d) Repeated 2x reflow (2nd time) at customer's place using
standard profile used for assembly of this part.
Electrical Testing (BBT) on bare PCB passed .
Based on the above trial, we feel that the failure seen is
not due to PCB failure.
4. This particular PCB is a 8 layer PCB, built using ISOLA FR370HR
material.
-----------------------------------------------------------------
Please share your inputs and thoughts on the failure phenomenon and
how to ascertain if the failure is due to PCB or assembly.
Thanks in advance!
Best Regards,
U.Nagaraj
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
